A microarray of biological material means a device for detecting genes or proteins wherein a large number of fragments of DNA, RNA or protein, are immobilized on a small substrate in high density. Such microarray chip is applied to researches for analyzing DNA mutations, RNA expressions and functions of proteins for understanding function of genes in large scale.
The microarray of a biological material (hereinafter, Biochip) may be classified into cDNA chip, oligonucleotide chip and protein chip on the basis of size of biological materials immobilized thereon. Full-length open leading frames or expressed sequence tag(EST)s having more than five (5) hundred base pairs can be immobilized on the cDNA chip. Oligonucleotides consisting of approximately 15 to 25 base pairs can be immobilized on the oligonucleotide chip.
The biochip on which plasmid DNA probe, oligonucleotide probe or protein is immobilized is primarily used for detecting gene expression, protein activity and DNA mutation. The most general applications of DNA chip, are for observing the difference of RNA expression between normal cell and abnormal cell. For example, researches for analyzing the difference of RNA expression between human normal cell and cancer cell are performed. Various studies employing high-density oligonucleotide chips, have been performed to analyze the type and system of gene expression of Saccharomyces cerevisea of which total six (6) thousand genes had been fully discovered.
Meanwhile, probes microarrayed on the biochip, are plasmid DNA comprising cDNA, products of polymerase chain reaction or synthetic oligonucleotide.
Probes can be microarrayed on the substrate through photolithography (Affymetrix Inc.), non-contact printing method using Ink-Jet injection process (Piezoelectric printing; Packard Instrument Inc., Syringe-solenoid printing; Cartesian Techonologies), contact printing method (Quill and Splite Pin; Telechem International Inc., Pin and Ring; Genetic Microsystem, Capillary pin; Bioneer Corp.) and so on.
However, whatever microarraying method is used, the amount of probes arrayed in each spot or in each biochip cannot be uniform and also the feature of spot microarrays can not be regular due to the effects caused from types of slide glass, electric noise generated in measuring wavelength and evaporation of spot.
More specifically, the direct synthesis of oligo-type probes on the substrate through photolithography process has critical problem that oligomers thus prepared on the substrate directly are not homogeneous even in same spot due to the failure of synthetic reaction.
Further, the fluctuation of the amount and feature of microarrayed probes may cause critical error especially in interpreting results of observing the difference of RNA expression pattern. The uniformity and regularity of microarrayed probes also should be secured in case of a biochip used for detecting DNA mutation accurately.
Furthermore, the control of the above uniformity and regularity are very important for the research on that DNA mutation or RNA expression should be observed continuously through same probes by using several biochips.
Therefore, the step for controlling the uniformity and regularity of the amount of probes should be necessarily added to a process for manufacturing biochip. In the addition, it is needed to provide the correction factor that indicate such differences between microarrayed for the bio-chip users in order to secure high fidelity of a bio-chip test result through the correction of the hybridization results.
Therefore, the primary object of the present invention is to provide a process of quality examining for microarray of biological material, which comprises a step for mixing probe and a compound which emits light or heat and does not react with said probe, a step for microarraying the mixture obtained in step 1) on a substrate, and a step for measuring light or heat emitted by the scanning of each spots of the microarray mixture.
The other object of the present invention is to provide a microarray of biological material wherein a mixture of probes and a compound which emits light or heat and does not react with said probe, is micrroarryed on substrate.